Stabilization of haloalkanes with fluoroethers of the type



United States Patent 3,278,615 STABILIZATION 0F HALOALKANES WITH FLUOROETHERS on THE TYPE Rr-O-C R2 Eric R. Larsen and Ralph A. Davis, Midland, Mich., and Jerry R. Lacoume, Lake Jackson, Tex., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Apr. 8, 1963, Ser. No. 271,508

6 Claims. (Cl. 260-652.5)

This invention relates to stabilized compositions of matter, and to a process for inhibiting the reaction of haloalkanes and metals such as aluminum.

It is well known that haloalkanes are attacked by metals such as aluminum and alloys containing aluminum. In the resulting reaction, the haloalkanes are polymerized and the aluminum is consumed. An effective stabilizer system is needed for these halogenated solvents because of the intended solvent uses, e.g., dry cleaning or vapor degreasing. Trichloroethylene and perchloroethylene, for example, are frequently used for degreasing metals such as aluminum and iron. With uninhibited solvents, metal chlorides are formed in the degreasing operation and act as catalysts for the further decomposition of the solvent. This decomposition of the solvent results in the formation of tars which are deposited upon the metal parts.

It is an object of the present invention to provide stabilized haloalkane solvents. A further object of the invention is to provide a method for reducing the decomposition of haloalkanes by metals such as aluminum.

It has now been discovered that these and other objects may be accomplished by incorporating an inhibiting amount of a fluorinated ether into the haloalkane solvent.

The fluoroethers which are employed as inhibitors are saturated compounds characterized by the presence of a difluoromethylene group which is attached to an ether oxygen atom. These compounds may be represented by the formula wherein each of R and R are organic groups of from 1 to carbon atoms or halosubstituted organic groups of from 1 to 10 carbon atoms. R is preferably a lower alkyl group of from 1 to 4 carbon atoms (methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl and sec.-butyl), a corresponding lower haloalkyl group (wherein the halo moiety is Cl, Br, I or F), a lower alkoxyalkyl group with a total of from 2 to 8 carbon atoms (such as 2- methoxyethyl, 3-ethoxypropyl or l-methoxyethyl), or the corresponding halogenated lower alkoxyalkyl groups of from 2 to 8 carbon atoms in which each alkyl group contains from 1 to 4 carbon atoms (such as 2,2,2-tri(2- chloro-1,1,Z-trifiuoroethoxymethyl)ethyl group and the 2-(dichloromethoxy)ethyl group). Typical fluoroethers which may be used as inhibitors for haloalkanes include 2-chloro-1,1,2-trifiuoroethyl methyl ether, 2-chloro-1,1- difiuoroethyl methyl ether, 2-chloro-1,l,2-trifluoroethyl 2, 2,2-trifluoroethyl ether (2,2,2-trifluoro-1-(2-chloro-1,1, 2-trifluoroethoxy)ethane), 2 bromo-1,1,2-trifluoroethyl methyl ether, 2,2-dichloro-1,1-difluoroethyl methyl ether, 2-chloro-1,1,2-trifluoroethyl chloromethyl ether, 2,2-dichloro-1,1-difluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl sec.-butyl ether, 2,2-dichloro-1,1-difluoroethyl isopropyl ether, 2,2-dichloro-1,1,2-trifiuoroethyl trichloromethyl ether and tetrakis[2-chloro-1,l,2-trifiuoroethoxymethyl]-rnethane. R is suitably a halogenated (F, Cl, Br, I) lower alkyl group of from 1 to 4 carbon atoms; at least one of the halogen atoms is preferably different from fluorine (i.e., a Cl, Br or I atom). R may contain from 1 to 9 halogen atoms. Examples of suitable R groups include trichloromethyl, tribromomethyl, difluoromethyl, iododifluoromethyl, 4,4-dichlorobutyl, 2, 2-dichloro-1,l,2-trifluoroethyl and 3-chloro-2,2-dibromo- 1,1-difluoropropyl groups. Other suitable fluorine-containing ethers which may be used as inhibitors are dis closed in US. Patents 2,803,665 and 2,803,666 to Miller et a1.

The ability of fluoroethers to prevent the reaction of aluminum and haloalkanes is a general property of saturated fluoroethers. Concentrations of the fluoroethers of up to about 25 volume percent may be used, but generally, from 0.1 to 20 volume per-cent of fluoroether is sufficient to inhibit the decomposition of the haloalkane by aluminum. Only an inhibiting amount of fluoroether stabilizer is required and amounts of fluoroether less than 0.1 volume percent give only very slight inhibition against metal-solvent reaction. Typical haloalkanes which may be stabilized by the addition of fluoroethers include carbon tetrachloride, carbon tetrabromide, nbutyl bromide, bromochloromethane, bromotrichloromethane, dibromodichloromethane, dibromodifluoromethane, ethyl bromide, lauryl bromide, methyl bromide, methylene bromide, trimethylene chlorobromide, chloroform, 1,1,1-trichloroethane, 1,1-dichlo-roethane, ethyl chloride, isopropyl chloride, methyl chloride, methylene chloride, 1,1,2-trichloroethane, 1,2-dibromo- 1,1-dichloroethane, 1,3-dibromo-1,l,2-trichloropropane, Lchloro-Z-bromoethane, 1,2-dibromo 3 chloropropane and 1,1,1-trichloro-3-bromopropane. While any haloalkane which attacks aluminum may be successfully inhibited by incorporating up to about 25 volume percent of saturated fluoroethers, the inhibitors are most advantageously employed with commercially useful haloalkane solvents. Thus, haloalkanes with from 1 to 20 carbon atoms (and preferably from 1 to 4 carbon atoms and up to 10 halogen atoms) with up to 20 halogen atoms (Cl, Br. I, F) in the molecule form a particularly important class of commercial solvents which may be stabilized with saturated fluoroethers.

One method of preparing the fluoroethers used as inhibitors and stabilizers in the present invention is by the base catalyzed addition of an alkanol or haloalkanol to a polyfiuoroalkene. Such a method is disclosed by Hanford et al. in US. Patent No. 2,409,274. Another method is by the reaction of polyhaloalkyl ethers (such as pentachloroethyl methyl ether) with antimony trifiuoride to form fluorinated ethers (such as 1,1-difluoro- 2,2,2-trichloroethyl methyl ether). Still another method of preparing suitable fluoroether inhibitors (such as 1,1,2,Z-tetrafluoro-2-bromoethyl methyl ether and 1,1, 2-trifiuoro-2,2-dichloroethyl methyl ether) involves the selective replacement of bromine atoms in an ether compound (such as 1,2,2-trifluoro-l,1-dibromoethyl methyl ether and 1,Z-dibrorno-1-fluoro-2,2-dichloroethyl methyl ether) with fluorine atoms using aspecialized fluorination agent such as bromine trifluoride (BrF The use of saturated fluoroethers as stabilizers and inhibitors to retard the reaction of haloalkanes and aluminum offers several advantages over other inhibiting systems. For example, the fluoroethers are relatively non-toxic, have a low degree of flammability, have a wide variety of boiling points (so that the fluoroether inhibitor can be chosen to closely match the boiling point of any given haloalkane solvent), have low water solubility (and ture (16-30 C.). The results are summarized in are, therefore, not extracted by water), have a low degree Table 1.

TABLE 1 Example Volume Percent of Number Haloalkane CH3 CFz CH ClF Result Inhibitor or H I 0 Slow reaction, solution I Br- C C-Br black after 16 hours.

Cl H 1 9. 1 N 0 attack after 240 hours.

H H H 0 Slow reaction, solution black in 16 hours. II BrCCCCl I I 9.1 No attack after 240 H Br H hours.

Cl H H 0 Slow bubble formation,

I I solution black after 240 III Cl C(|Z-('3Br hours.

Cl H II 9. 1 N 0 attack after 240 hours.

Solution dark brown H H 0 after 16 hours; black I I after 240 hours. IV Cl C- CBr 9. 1 N 0 attack after 240 H II hours.

1 1 ml. of inhibitor to ml. of alkane.

of chemical activity, are hydrolytically stable and are not oxidized by oxygen or ozone.

In addition, the fiuoroethers are particularly useful as inhibitors and stabilizers because they have been found to be effective in both the liquid and vapor state. Various mixtures of fiuoroethers may be used to tailor the inhibitor properties to the particular haloalkane solvent.

The following examples are submitted for the purpose EXAMPLES V-VIII It is known that CBrCl CHClBr reacts much more violently with aluminum foil than does CCl CH Therefore, CBrCl CHClBr was employed as the haloalkane to be stabilized in order to provide a more stringent test of the inhibiting power of the fiuoroethers. The experiments were conducted as in Examples I-IV and the results are summarized in Table 2.

TABLE 2 Example Number Fluoroether Inhibitor Volume Percent Concentration of Fluoreether in Haloalkane (BIClzC CBrClI-I) Result CHaO CFZCHCIF Aluminum destroyed 1 minute after being scratched.

No attack after 240 hours.

Aluminum destroyed 1 minute after being scratched.

N 0 attack after 240 hours.

N 0 attack after 240 hours.

C Ha H Aluminum destroyed 1 minute after being scratched.

N 0 attack after 240 hours.

VIII

Aluminum destroyed 1 minute after being scratched.

No attack after 240 hours.

1 Saturated solution.

of illustration only and are not to be construed as limiting the scope of the invention in any Way.

EXAMPLES I-IV Squares of commercially available aluminum foil (one inch by one inch) of approximately .001 inch in thickness were placed in the various samples of polyhaloalkanes containting the indicated amounts of 2-ch1or-o-1,1,2.-trifluoroethyl methyl ether (CH OCF CHCIF) and the aluminum foil scratched with a knife to initiate the reaction. All reactions Werecarried out at ambient room tempera- EXAMPLES IX-XIII entamoun'ts of Z-chlo'ro-l,l,2-trifiuoroethyl methyl ether (CH OCF CHClF). The solutions were brought to reflux and, after forty minutes; the surface of each strip EXAMPLES XVII-XX Ina manner identical with the procedure employed in Examples, I-IV, 1,1,2;2'-tetrafluoro-2-bromoethyl methyl g i i ifigi g g ggg spatula The results J ether and 1',l,2-trifluoro-2 2-dichloroethyl methyl ether I 5 were dissolved. in l,1,Z-trichloro-lyZdibromoethane (one TABLE milliliter of ether in milliliters of haloalkane', a 9.1 'volume percent solution) and a strip of. aluminum foil Volume Percent Concentra- Example tion oiFluoroether Exposure Weight Loss added The foll was Scratched torn 3 stamless Number (CH3OOF2CHC1F)I11 Time(hours) (grams) steel spatula and allowed to stand 1n the inhibited halo- Hamlkane (C01!) 10 alkane at ambient room temperature for a' 48-hour. period. No reaction was observed. A. slight yellowing of the 4 8' inhibited solution occurred due tov the photo decomposi- 7..4. 144 0 tion of :l,1,2-trifluoro-1,2-dibromoethane. The test was Hg 30001 repeated using methyl chloroform in; place of 1,1,2-

trifluoro-1,2-d1bromoethane. No corrosion occurred after 1 Reaction with the aluminum alloy started immediately after scratch. 24'hOuI p The results Summarized inTable TABLE 5 Example Haloalkane Inhibitor and Volume Result Number Percent Concentration ('31 (I31 XVII BI(IJ$H CHsOCFzC F1131, 9.1 No attack after 48 hours.

Cl Br 01 (I31 XVIII BrCO-H OH3o0F2CFo1;,9.1 Do.

Cl Br 0 ClsCHa CHaO CF F2131, 9.1 No attack after 24 hours.

CChCHa CH3OCF2CFC1z,9.1 D0.

As shown by Table 3, the reaction between the aluminum alloy and carbon tetrachloride Was completely prevented by the fluoroether (CH OCF CHCIF) inhibitor.

I EXAMPLES XIV-XVI We claim as our invention: 1. A stabilized haloalkane which contains a stabilizing amount of a saturated fiuoroether of the formula wherein:

(a) R is selected from the group consisting of lower alkyl, lower haloalkyl, a lower alkoxyalkyl group wherein each alkyl moiety contains from 1 to 4 carbon atoms, and a lower halogenated alkoxyalkyl group of from 2 to 8 carbon atoms, and

(b) R is a lower haloalkyl group.

TABLE 4 Volume Percent Concentra- Total (Cu- Total (Cumulative) Example Number tion of Fluoroether mulative) Ex- Weight Loss (Grams) (CHQOCFZCHCIF) in posure Time Haloalkane (CH CC13) (Hours) 3.0 (194 m1. of CH CC13 and 0 6 ml. of CHaOCFzCHClF) XIV (Strip mounted in vapor). d 17 0.0005. 23 0.0007. do 39. 5 0.0008. 3.0 (194 ml. of CHaCCl and 0 6 ml. of CHsOCFzCHClF). XV (Strip mounted in refluxing d 17 0.0009. liquid). 23 0.0013. 39. 5 0.0020.

0 Indication of attack within 1 minute after exposure to hot vapors.

XVI (Strip mounted in vapor) 0 0.5 0.8303-Solution black,

corrosion had proceeded to a point that allowed strip to fall into refluxing liquid.

Table 4 shows that the fiuoroether inhibitor is effective in both the liquid and vapor state.

2. Stabilized 1,2-dibromo-1,1,2-trichloroethane which contains a stabilizing amount of an ether selected from 7 the group consisting of 2-chloro-1,1,Z-trifluoroethyl methyl ether, 2,2-dichloro-1,1,2-trifluoroethyl trichloromethyl ether, 2,2-dichlorol,l-difluoroethyl isopropyl ether and te-trakis [2-chloro- 1, 1,Z-trifluoroethoxymethyl]-methar1e.

3. Stabilized carbon tetrachloride which contains from 0.1 to 25 volume percent of 2-chloro-1,1,2-trifluoroethyl methyl ether.

4. Stabilized methyl chloroform containing from 0.1 to 25 volume percent of 2-chloro-1,1,2-trifluoroethyl methyl ether.

5. A method of retarding the reaction of haloalkanes and metal which comprises contacting said metal with a haloa-lkane in the presence of a fiuoroether of the formula of claim 1.

6. A method of retarding the reaction of haloalkanes 15 with aluminum which comprises contacting aluminum with a haloalkane in the presence of a fiuoroether of the formula wherein:

(a) R is selected from the group consisting of lower alkyl, lower haloalkyl, a lower alkoxyalkyl wherein each alkyl moiety contains from 1 to 4 carbon atoms, and a lower halogenated alkoxyalkyl group of from 2 to 8 carbon atoms, and

(b) R is a lower haloalkyl group.

References Cited by the Examiner UNITED STATES PATENTS 2,371,645 3/1945 Aitchison et a1. 260'-652.5

2,818,446 12/1957 Starks 260-6525 LEON ZITVER, Primary Examiner.

DANIEL D. HORWITZ, Examiner.

20 M. M. JACOB, Assistant Examiner. 

1. A STABILIZED HALOALKANE WHICH CONTAINS A STABILIZING AMOUNT OF A SATURATED FLUOROETHER OF THE FORMULA 